Suspected Taleban militants have killed three Afghan soldiers in violence overnight in the south-east, the authorities say.
Up to 200 fighters are said to have taken part in the attack on a district headquarters at Terwah in Paktika province near the Pakistan border.
"They set the police station on fire, took four of our men and fled to Pakistan," provincial police chief Dawlat Khan told the Associated Press.
Hours earlier, at least 22 people died in a gun battle in nearby Birmal district, six of them Afghan troops.
The others killed are suspected of having links to the former Taleban regime.
Meanwhile, in neighbouring Zabol Province a new governor took office on Monday as part of President Karzai's attempts to extend his influence in the south.
Mr Karzai has announced a change of governors in Zabol and Kandahar, both provinces where anti-government Taleban insurgents have been active in recent months.
The outgoing Zabol governor, Hamidullah Tokhi, said the orderly transfer of power in Zabol was a good sign for Afghanistan's future.
But he added that President Karzai would have to supply more money for local salaries - and the new governor, Hafizullah Khan, who is not from Zabol, would still have to win the respect of local officials.
The BBC's Ian MacWilliam, who is in Kandahar, says there is some local opposition to the changes of governor among tribal leaders in Kandahar and Zabol, but they have agreed to go along with the central government's plans.